Current-controlling means for electric circuits



Jam. i6, QZZ I Alf/Il@ G. A. ANDEREGG, CURRENT CONTROLLING MEANS FOR ELECTRIC CIRCUITS.

FILI-:D JUNE 30, 1917.

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GUSTAVUS A. ANDEREGG, OF OAK PARK, ILLINOIS, ASSGNOR TO WESTERN' ELECTRC COMILANY, LENCORPORATED, OF NEW YORK, N. Y., A CDRPORAEON 0F NEVI YORK.

Application filed June 30,

To all whom t may concern.'

Be it known that l, Guerin/'Us A. ANDER- ncc, a citizen of the United States, residing at Oak Park, inthe county of Cook and State of Illinois, have invented certain new and useful Improvements in Current-Controlling Means for Electric Circuits, ot which the following is a full, clear, concise, and exact description.

This invention relates to electric circuits and apparatus for controlling current therein, and more particularly to circuits comprising reactors or reactance coils or such apparatus in combination with condensers.

Heretofore reactors or reactance coils having constant inductances have been used for the purpose oit current control. The primary purpose, however, for using such coils was to guard against sudden transient impulses of current or against current of other than the fundamental frequency. Such coils'were operative to limit the flow of current of fundamental frequency, only because of the fact that a greater amount of voltage is consumed in the coil when the current increases therein. Such increase in voltage consumption is represented by the well known formula that,

Ezels-LI (i) where E is the voltage required to force a current l' of frequency f through a reactance coil having an inductance L. From formula (l), it is clear that the voltage consumed in such a coil is directly proportional to the current passing therethrough. lVhile such a degree of protection may be satisfactory 'for some classes or" ser rice. there are inany instances where it is not so.

Again for other classes of service, reactors or reactance coils, such as have heretofore been known, cannot be used, due to the impedance thereby introduced into `the circuit under normal operating conditions. lVhere suchis the case, it has been proposed to neutralize this impedance by means of a condenser connected, in series with the reactor or reactance coil. The protection thus gained is a gain only 'against currents ot 1917. Serial No. 178,000.

other than the fundamental frequency, no protection whatever being obtained against current ot the fundamental frequency. This is due to the fact that the leading counterelectroinotive force of the condenser is affected by any cha-nge ot the current equally with the counter-electromotive force oi' the reactance coil, which is lagging with respect to the current. l

An object ot' this invention is to overcome the hercinbefore mentioned difficulties and in accordance with one feature of this invention, a reactance coil is provided whose inductance changes rapidly with change of current passing through its windings. rl`his result is preferably accomplished by makingl the. core ot such material that its permeability increases rapidly wit-h increase of current through the coil windings. in other words, so that a slight increase oit current produces a large increase in permeability. Thus, a slight increase ot current above the limit predetermined by the design of the apparatus, in response to an increase of voltage across the terminals of the coil. produces so great an increase in inductance due to the coil that the product ot the inductance ll and 'the current l, and therefore the voltage consumed in the coil, increases so rapidly that the .voltage to which the rest oli the apparatus in the circuit is subjected is not unduly increased.. notwithstanding a considerable increase may occur in the total Voltage impressed on the circuit. ln accordance with another feature. the reactance coil is associzzted with a condenser in such a way to offer any desired impedance to a current oli given frequency and amplitude. Since the capacity of the condenser is practically unaffected by change ot current, anyY change ci? amplitude oi the current will (listurb the balance between the reactances ot the coil and the condenser, and a corresponding change in the impedance oithe circuit, even to the fundamental frequency, will thereby result.

This invention will be more clearly understood by reference to the drawings, wherein Fig, l shows the preferred embodiment oi' the invention. consisting of a condenser, a reactance coil and a telephone receiver functioning as a detecting means in an alternating current lNheatstcne bridge circuit; Fig. 2 is a graphical representation of the change of impedance of such detector circuit due to change of voltage impressed thereon; Fig. 3 shows similarly the amount of current produced. in the detector circuit by various values of voltage applied across its terniinais; while Figs. 4l. 5 and 6 show various modifications hereinafter to be described.

In the preferred embodiment of the invention, a telephone receiver 5 may be connected in series with a condenser 6 and a reactance coil 7, across the terminals 8 and 9 of an alternating current YWheat-stone bridge circuit. Fluch bridge circuit may be schematically represented by non-inductive resistance branches l0, l0; a coil ll to be tested; and a balancing arin comprising a resistance l1Q and an. impedance 13. Testing current may be supplied by an alternating ourrent j. nerator lll. ln ordinary operation, the resstancc arms l0, l0; the resistance l2 and the impedance are pern'iancntly connec' f to the generator i4. rThe 'testing coil .ll i..7 of course, necessarily removable in order to provide for the insertion of different coils to be tested. When the bridge is perfectly balanced. there is, as is well known. no difference of potential between the terminals 8 an(v SA and consequently no tendency for current to flow through the detector circuit. lllien the coil ll. is removed, however, there is a relatively large difference of potential between the terminals 8 and 9 of the detector circuit. and consequently tendency for a large amount of current to flow through the receiver 5. Such large diiference of potential between the terminals 8 and 9 may also result from short-circuiting the coil lll. lVere the detector circuit not provided with a condenser 6 and a reactance coil. Y whose inductance changes rapidly with change of current in the coil, this current would be of such magnitude as to cause an excessive amplitude of vibration of the receiver diaphragm, which would be injurious to an observer if he happened. to have the receiver held closely to his ear. ln fact. it has been found that the disturbance, due to the. accidental removal or short-circni ing of the test apparatus lla may be so great as to incapacitate the observer for a considerable period 0f time,

The effect of including the condenser (3 and the reactance coil 7 in the detector circuit is clearly shown by Figs. 2 and 3, wnich are true representations of the results of measurements mac e on an actual testing circuit. shown in Fig. l. ln Fig. 2. curve fr represents the impedance of the circuit through the receiver 5 for various values of voltage between the terminals 8 and 9 when the condenser 6 and the reactance coil 'T are omitted; while curve B represents the impedance of the. same circuit7 when the condenser G and the reactance coil 7 are included in it. Curves A and B of Fig. 3 show the correspondingr values of' current fiowing through the receiver 5. lt is to be noted fromA Fig. 2 that at small values of voltage across the terminals 8 and 9, the impedance of the detector circuit is even less than that of the telephone receiver alone. This is actually what is desired, since the highest sensitivity of the detector circuit is required when t-he bridge circuit is most nearly balanced.

lt has been found in the actual testing cin-uit hereinbefore mentioned that currents up to approximately 0.0018 ampere'do not cause an injuriously loud tone in the receiver. By referring to Fig. 3, it is seen that approximately five volts across `the apparatus, that is, between the terminals 8 and 9 would cause this amount of current, were the projective apparatus not in use (see curve it) while about sixty volts would be required to produce the same amount'of current when such apparatus is being usedA (see curve B). Thus the observer is amply protected against any voltage which it is desir able and necessary to use in actual operation.

and of the condenser G, could moreover easil be cha-need in order to increase the .vi e

The constants of the reactance coilV forcesfat a frequency of 900 cycles per f second. rflic winding consists of 2000 turns of insulated copper wire wound uniformly upon the core having a mean length of approxiniately twenty centimeters and a cross sectional area of a proximately three` square centimeters. For an alternating cur-` rent of 0.000%A ampere, such a coil has an in-k dwtance of approximately 1.7 henrys, while for a current of 0.0015 ampere its induc tance is approximately 5.8 henrys. 'A condenser having a. capacity of approximately 0.016 n'lirrofarad has been vfound suitable for use with such coil.` l Y The modification of Fig.- lmay also be to limit the ramount of current in a Vreused ceiver or other energy transforming device o. By suitably choosing the constants of the condenser 6 and reactance coil 7, the im` pcdance of the parallel circuit, of whichV they form the branches7 may be -m'ade exceedine.v1

currentso may provide a' high impedance V,shunt high for very small values ofA fiowine; through the receiver 5, and` refiaeco thereabout. iny increase ot voltage across the terminals 15 and 16 will cause this impedance to decrease rapidly, due to the change ot inductance of the reactance coil 7, thereby placing a comparatively lovv impedance shunt about the receiver 5. This increased current flowing' from the generator i4'.- through an impedance coil or other apparatus 1T, Will limit the voltage attainable between the terminals 15 and 16 and hence the current through the receiver 5.

1n the modification oi',l Fig. 5 a condenser l5 and reactance coil are connected in parallel with cach other.y and in turn in series with a receiver or other energy transforming apparatus 5. This combination may be supplied with power trom a generator 14 through an impedance coil or other appa ratus 17. A suitable condenser arranged in this Way with a suitable coil Whose. inductance changes greatly ivlith change ot current in its Winding may be used to provide a circuit having very high impedance for some predetermined chosen condition of voltage. or current and a lower impedance `tor all other conditions oil' voltage or current.

The modification of Fig. 6 consists of a condenser 6 and a reactance coil 7 connected in series with each other and in turn in parallel with a receiver or other energy transtorming apparatus 5. This combination likewise may be supplied with power trom a zgenerator 14 through an impedance coil or other apparatus 17. This arrangement using a suitable condenser in connection with a suitable coil Whose inductance changes greatly with change of current may be used to produce a low impedance shunt around any desired apparatus t'or some predetermined condition ot current or voltage. The shunting etl'ect ot the condenser and reactance coil in series will then be less tor any other conditions et voltage or current.

ther conditions than those hereinbefore mentioned may obviously be met by suitably choosing the constants of the condenser and reactance coil, and all such combinations wherein a reactance coil, Whose inductance changes rapidly with change of current in its windings, is used, either alone or in combination with a condenser, clearly come within the scope of this invention.

lVhat is claimed is:

1. An electrical circuit comprising a .source et current. a detector responsive to normal values ot the current from said source` and means tor protecting said de the,

`very rapidly with changes in strength of the current tlowing through the coil.

:2. in electrical circuit comprising a source ot alternating current. a detector responsive to current trom said source and designed to operate Within a `given range oi current strength, and means tor protect ing; said detector from frequencies substantially ditl'erent from the normal frequency ot' said source and Yfor protectin said detector from substantial changes in the root mean square value ot the current supplied by said source, said means comprising a closed magnetic circuit reactance coil in cir cuit. with said source and said detector.

25. 1n an electrical circuit comprising; a source ci alternatingl current, a detector re* sponsive to current from said source and designed to operate Within a `given range or current strength, and means tor holding substantially constant the root mean square value ot' the current supplied to said detector regardless oi' Wide variations in the voltage supplied by said source, said means comprising a condenser and a closed magnetic circuit reactance coil in circuit with .said detector. said condenser and coil havingv such values as to resonate at a frequency present in said circuit.

t. sin electrical circuit comprising a source o'l' alternating` current, a detector responsive to current from said source and designed to operate vithin a given range of current strength, and means for protecting;r said detector from substantial changes in the root mean square value of the current supplied to said source. said means comprisingl a condenser and a closed magnetic circuit reactance coil in circuit with said detector, said condenser and coil rcsonatine; at the normal frequency of said source.

An electrical circuit comprising a source ot alternating current, a detector in circuit with said source and designed to operate Within a `given range of current strength, and means tor holding,r substantially constant the drop in potential across the terminals ot said detector regardless oi" Wide variations in the voltage supplied by said source, said means comprising a condenser and a closed magnetic circuit reactance coil in series with each other and in series with said detector. said condenser and coil ha vving` such values to resonate at the 'frequency of said source for a strength ot current supplied by said detector Ywhich is Within the permissible range.

G. A testing circuit tor testing the characteristics oi' electrical apparatus comprisinga VVheatstone bridge circuit including the apparatus to be tested, a source of alternating current associated With the bridge, a detector responsive to small iiuctuatingr currents to determine when the bridge is in balanced condition, said detector being` designed 'm operate Within a given range of Current strength,A and means for preventinga substantial unhalaiice of said bridge from causing current to flow through said receiver of a greater strength than is permissible, said means Con'iprising a closed magnetic circuit. reaetunce coil, the core of Which is vompose Of a. material, the permeability of which changes very rapidly with changes in the strength of the current flowing through the coil. y

in Witness whereof, I hereunto subscribe my name this 26th dav of June, A. D., 1917.

GUSTAVUS A. ANDEREGG. 

